Dr. MartensMaple Zip womens Construction Boot

Are the sizes to select in uk or us?

I am confused. nowhere on the details does it say if these are ordered by uk or us sizing. which size do i order if i’m a us10?

What if I am a 6.5? What’s best way to go bigger size or smaller?

How heavy do the boots feel, could you work in them 10hr/day, 4x/week??